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Cells211 - Cells 1 That Living organisms are composed of...

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Cells – 1 That Living organisms are composed of one or more cells is one of the unifying principles of biology. A cell is a unique compartment, composed of molecules organized into a structural and functional unit and separated from the external environment by a membrane boundary. The cell is the smallest unit of life. Our oldest cellular fossils date back 3.5 billion years and oxygen-producing cyanobacteria are found in 2.5 billion year old stromatolite fossils in Australia (where living stromatolites are found, too). Living and Fossil Cyanobacteria Fossil and Living Stromatolites For single-celled organisms, all requirements for life: growth, development, regulation, reproduction and interactions with their environment are met within a single cell. Multicellular plants, fungi and animals are comprised of collections of cells and tissues, each with specialized structures and functions that contribute to the whole. These two statements: (Living organisms are composed of cells and cells are the structural and functional unit of life) along with a third: all cells come from pre- existing cells, form the cell theory. In this chapter, we will see how the structure of cells and, in particular, the structure of cell components, facilitates the functioning of cells. Learning about cell structure and function is challenging. Cells, for the most part, are microscopic. Moreover, when we turn to the functioning of cells, and their component parts, the organelles, we often affect the very structure we are hoping to learn about with our manipulations. Until the first light microscopes 400+ years ago, no one had really seen cells. However, even the best light microscope can not clearly resolve images magnified more than 1000x times (for detail about 0.2 ± m.) There are a variety of methods used to enhance the quality of images viewed with a light microscope, which, in combination, can help researchers. Some examples are illustrated in your text. Many cell components that we discuss today were not known or seen prior to the use of electron microscopes. Electron microscopes can resolve images of about 2 nm. The scanning-tunneling microscope can generate computer surface images of single atoms magnified about 2 million times. Bellevue College is fortunate to have a scanning electron microscope donated for student (and faculty) use by a local resident.
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Cells – 2 Cell biologists frequently study cell components outside of the cell using techniques such as cell fractionation, in which differential centrifugation is used to separate and isolate different organelles based on their density. Once isolated, organelles can be studied in more detail, which helps students learn and understand more about cell structure and function. We start our discussion of cells by cataloging the common features of all cells.
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